1. Field of the Disclosure
The present disclosure relates to an input device, and particularly relates to an input device capable of returning from an erroneous detection due to a foreign substance or the like.
2. Description of the Related Art
Conventional capacitance-type input devices can determine an operation position by detecting a change in capacitance accompanied by an operation. However, in such capacitance-type input devices, a change in temperature, for example, causes the detection value thereof to be changed, and thus malfunction may occur.
Operations of the input device disclosed in Japanese Unexamined Patent Application Publication No. 2012-048340 will be described with reference to FIG. 5. FIG. 5 is a flow diagram illustrating operations of the input device disclosed in Japanese Unexamined Patent Application Publication No. 2012-048340.
As shown in FIG. 5, sensor output values are acquired periodically (step S901), and it is determined whether a predetermined time serving as conditions for performing a correction coefficient update process has elapsed (step S902). When it is determined that the predetermined time has elapsed (step S902: YES), it is determined whether the sensor output value is equal to or more than a touch determination threshold (step S903). When it is determined that the sensor output value is less than the touch determination threshold (step S903: NO), a determination threshold change flag F1 is set to “0” (step S908), and the process proceeds to step S909.
In step S903, when it is determined that the sensor output value is equal to or more than the touch determination threshold (step S903: YES), it is determined whether event occurrence information composed of identification information is notified (step S904). When it is determined that a push event notification is not performed, a push event is notified (step S905). When the push event is notified, the process proceeds to step S906 as it is. Thereafter, the determination threshold change flag F1 is set to “1” (step S906), and a difference value between the sensor output value and a predetermined reference value (“512” in an example of the related art) is calculated as a correction coefficient A1 (step S907).
Next, a stored correction coefficient is updated (step S909). Thereby, the content of the correction coefficient is updated so that the sensor output value is set to be equal to the predetermined reference value.
As stated above, in order to suppress a malfunction due to a change in temperature, the detection value is replaced by a new reference value when the operation is not detected, and the sensor output value and the predetermined reference value are replaced by new reference values when the operation is detected. With such a configuration, it is possible to suppress the influence of the detection value caused by a fluctuation in capacitance due to the temperature change.
However, when the operation is detected, the difference value between the sensor output value and the predetermined reference value are set to a new correction coefficient, and the correction coefficient is updated. Therefore, a correct operation can be performed following a fluctuation such as the temperature change. However, when a foreign substance such as, for example, hard currency is placed on the input device, and a touch is detected erroneously, there is a problem in that an output signal indicating an operation until the foreign substance is removed is continued and hence the return from the erroneous detection is not possible.
These and other drawbacks exist.